The present invention broadly relates to weaving machines and, more specifically, pertains to a new and improved construction of an apparatus used in shuttleless weaving machines where the filling insertion takes place on one side by means of gripper systems provided with clamping means for the filling-yarn or weft thread and which are advanced into the shed and then retracted.
Generally speaking, the apparatus of the present invention is employed in a shuttleless weaving machine wherein filling-in yarn or weft thread is inserted by gripper systems which are bilaterally advanced into the shed and then retracted and which are provided with clamping means for the filling-yarn. Control means are arranged laterally of the weaving machine for processing ends of the filling-yarn before and after insertion thereof into the shed, for constrained actuation of the clamping means by control levers controlled by cam means and entering through the warp threads of the shed from the exterior.
Such a weaving machine is known, for instance, from German Pat. No. 1,710,292, granted Aug. 30, 1973. In this patent, the filling-yarn is seized by the clamping means of a gripper system when outside of the shed and is transported by the gripper system to the approximate shed center. There, the filling is transferred to the clamping means of a gripper system advanced from the opposite side which, upon retraction, pulls the filling-yarn entirely through the shed. The yarn transfer at the center of the shed takes place while the participating clamping means are controlled in a constrained manner in such a way as to provide a brief time during which control levers pass through the shed's warp threads to open and then again close the clamping means. The actuation of the control levers is coupled to the main drive for the weaving machine and takes place not only when the filling-yarn is transferred in the shed's center, but also can be used when seizing and releasing the filling-yarn outside of the shed.
The control system is designed in such a manner that the control lever is pivotably supported on the end of arms which themselves are rigidly seated on the sley shaft and accordingly carry out a pivoting motion together with the sley during the beating-up of a filling-yarn. A pivot lever acting as a support for sensor rolls is furthermore rotatably seated on the sley shaft, where the sensor rolls rest under spring loading against a cam. The cam is mounted on a special, continuously rotating side shaft parallel to the sley shaft. The connection between the control lever and the pivot lever is provided by a connecting rod. This continuously rotating side shaft rotating at 1:1 is parallel to the main shaft ensuring the power transmission of the reed and gripper drive from one side of the weaving machine to the other and advantageously rotates, for instance, in the ratio of 3:1 or 4:1. However, the geometry of weaving machines permits only a limited space for mounting and sizing the main shaft, the side shaft with cams and the sley shaft. In particular, it is impossible to select the cams so as to possess a sufficiently large size.
When beating-up, each above-mentioned arm not only carries along the control lever, but it furthermore, by means of a stop and driver, rotates the pivot lever, whereby the sensing roll is lifted from the cam. The spacing between the stop and the driver must be precisely set in order to achieve the proper motion of the control lever during reed beat-up.
It is characteristic of this equipment that at higher operating speeds of the weaving machine, the rolls no longer intimately follow the cam profile or cam bearing surface but lift off it and tend to bounce. As a result, they will also lift off in undesired manner from the control cam profile or surface against which they are supposed to bear in relation to the desired control curve. Because the control levers follow, via the connecting rod, the motion of the rolls, i.e., the motions of the pivot lever, the clamping means at the gripper systems may be spuriously actuated. Therefore, flawless filling-yarn transfer from one gripper system to the other is no longer assured in such a case. Moreover, the bouncing and reseating of the rolls greatly stresses, and possibly damages, the cam bearing surfaces.
German Pat. No. 2,934,474, granted June 11, 1981, and corresponding to the U.S. Pat. No. 4,384,598, granted May 24, 1983, describes a modified apparatus. In this apparatus, the pivot lever sensing the cam motion is rotatably supported but fixed to the machine outside the sley shaft. This design averts the above-cited difficulties and even at high operating speeds of the weaving machine, improved yarn transfer is achieved. In this design, the center of rotation of the pivot lever for driving the connecting rod and the control lever no longer is situated in the sley shaft and the roll no longer lifts off of the cam but, on the contrary, the rolls always remain on the cam's control curve. Furthermore, it is no longer necessary as previously to precisely set the costly and highly stressed bearing surface at the stop and driver. Moreover, an improved arrangement of the return spring is possible at the pivot lever, and no interfering inertial forces arise at the spring during reed beat-up.
Nevertheless, a further factor adversely affects both of the known apparatuses. This factor is that the control lever is mounted on the end of a special arm and, upon reed beat-up, is pivoted together with this arm out of the shed and back in addition to its own control motion. The number of required individual parts and bearing locations or joints results in a not insignificant amount of play. Due to the vibrations of the arms and of the control lever due to the brusque stopping motion of the reed, this play becomes noticeable at the control site, that is, at the end of the control lever, and may impair the control function.
Additionally, another problem arises. It has been noted in practice that at higher operating speeds of the weaving machine, the uncontrolled vibrations arising at the control parts due to the inertial forces exceed by far the actually required control force. Consequently, in these known designs, the springs of the cam sensor means always must be highly tightened. The high spring force results in excessive wear and furthermore constitutes an impediment when the weaving machine must be turned by hand.